EPIDEMIC POLIOMYELITIS 685 



only evidence, in fact, that such a condition is due to the virus 

 of poliomyelitis lies in the fact that subsequently the serum has 

 the capacity of neutralising the virus. It is to be noted that 

 serum containing antibodies is of little or no therapeutic value, 

 and animals injected with a neutralised mixture of virus and 

 antiserum do not thereby develop immunity against subsequent 

 infection. At present, attempts to treat cases of poliomyelitis 

 by antisera have been unsuccessful. It is stated by Kraus that 

 if the virus which has been killed by exposure to phenol is 

 injected into monkeys they develop resistance, but such a pro- 

 phylactic vaccine treatment requires further investigation. 



The means by which the disease originates and is spread 

 under natural conditions are still obscure. As has been stated, 

 its distribution is usually sporadic, and how such cases arise is 

 unknown. It has been found, however, that in monkeys 

 recovered from the disease the nasal mucosa remains infective 

 for many months after the virus has disappeared from the 

 central nervous system. This observation may be significant, 

 and it is likely that in man there are chronic carriers such as 

 exist in other diseases. The widespread occurrence of abortive 

 cases may also constitute the means by which infection is kept 

 up in a community. The frequent appearance of sore throat 

 as an initial symptom may indicate that the nasal and 

 buccal secretions are the means by which infection is trans- 

 ferred. Some observations have been put forward by Eosenau 

 pointing to a blood-sucking fly, stomoxys calcitrans, being 

 capable of transferring the disease in monkeys. The absence 

 of the virus from the blood in man rather militates against 

 infection by insects, but it may yet be found that this fluid at 

 some particular stage of the disease is infective. 



The fact that poliomyelitis appears under a variety of clinical 

 types makes the diagnosis difficult in many cases, especially of 

 mild illness. This is specially true of the meningitic type, which 

 may be difficult to distinguish from epidemic cerebro-spinal 

 meningitis, especially as the characters of lumbar puncture fluid 

 in the two diseases are very similar and, as is known, it may 

 often be difficult to isolate the meningococcus where it is actually 

 the causal organism. It may be stated that cases have occurred 

 where the diagnosis lay between poliomyelitis and the paralytic 

 type of rabies, and in the present stage of knowledge the sus- 

 ceptibility of the rabbit to the latter disease would constitute 

 the only means by which the diagnosis could be arrived at. 



Homer has described a paralytic disease in guinea-pigs closely 

 resembling human poliomyelitis. 



